1. Field of the Invention
This invention relates to an imaging apparatus, an image processing apparatus, an imaging method of an image processing apparatus and an image processing computer program.
2. Description of the Related Art
As a result of technological development in the field of digital camera, conventional OHPs (OverHead Projectors) for reading papers and OHP sheets by means of a line scanner and projecting images thereof have been and being replaced by those using a text/picture (document) camera that comprises a digital camera.
A document camera is adapted to pickup an image of the original placed on an original table by the user by means of a camera and the data of the original obtained by picking up the image of the original are stored in the memory of a computer and processed so that the original is enlarged and projected on a screen by means of a projector (see, inter alia, Patent Document 1: Unexamined Japanese Patent Application KOKAI Publication No. 2002-354331 (pp. 2-3, FIG. 1)).
Unlike conventional OHPs, such document cameras can pick up an image of a three-dimensional object and project an image thereof. Thus, they are replacing the conventional OHPs.
However, when the original is shot by a known document camera from an oblique direction, the edge of the original located close to the camera goes out of the view angle (shooting range) of the camera. The zoom magnification of the camera has to be reduced to avoid this problem.
Then, as a result the ratio of the area of the original to the total area of the picked-up image is reduced even if the image is subjected to keystone correction so that only a small image of the original is projected and the viewers will find difficulty in viewing the projected image. This tendency becomes remarkable particularly when the angle of camera movements is large.
Additionally, if the original is warped or distorted, the picked-up image may contain an unnecessary part. Then, if the image containing such an unnecessary part is processed for luminance, color difference and so on to improve the effects of the image, the image can be improperly processed and, if such an image is projected on a screen, again the viewers will find difficulty in viewing the projected image.
In view of the above identified problems of the prior art it is therefore the object of the present invention to provide an imaging apparatus, an image processing apparatus, an image processing method of an imaging apparatus and an image processing computer program capable of obtaining a clearly visible image.